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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

/74                                     MANGANESE DIOXIDE

chloride solution, are treated with 6 c.c. of ammonia and. any turbidity
formed within 12 hours noted.

4.  Heavy Metals, Lime.—The i : 20 solution is treated with hydrogen
sulphide and any turbidity noted, either before or after addition of ammonia
(heavy metals).

The same solution is treated wtih ammonium chloride in excess and
then with ammonium oxalate (lime).

5.  Ammonia.—5cc Stannic Chloride.

MgSO(] + 7Ha() --- 246-32

Colourless crystals, readily soluble in 1-5 parts of water. It may bo
contaminated with chlorides, phosphates, arsenic, copper, iron, xinc, alu-
minium, lime and alkalies.

1.  Solubility, Chlorides..........-The aqueous solution should be clear and

neutral and should not become, milky with silver nitrate.

2.  Phosphates.—5 grams, dissolved in, 35 c.c. of water and treated
with ammonium chloride and excess of ammonia., should give a. limpid
solution even after standing for hours.

3.  Arsenic.—I gram, treated with 5 c.c. of BettendoiTs reagent, should
not colour within an hour.

4.  Metals, Earths.-  -The i : :io solution should not change with hydro-
gen sulphide, or ammonia, or ammonium sulphide, or ammonium oxalato,
or potassium ferrocyanide.

5.  Alkalies.........i grain, dissolved in 30 c.c, of water, is boiled with 3

grams of  barium carbonate and  filtered:    the   fill rate  should   not   react
alkaline and should leave no appreciable residue on evaporation.




The product, of this composition of the greatest practical, importance
is the natural Pyvolusitc, which forms compact: masses or siua.ll irregular
pieces or more or less coarse powder. The mass has a, radiating crystalline
structure, a greyish-brown colour and an almost met al lie: lustre ; the powder
is black.

Pyrolusite often occurs mixed with other oxides of manganese, such as
Bmunite, manganic oxide ; Ilauxnumnilc., mixed nnuiganous-manganic
oxide; Mail finite, hydratcd manganic oxide; Pailomc/tui, manganous
oxide and manganese dioxide.

These minerals may contain also variable quantities of ferric oxide,
alumina, baryta, magnesia and silica (gangue), and small amounts of lead
or copper oxide, lime, alkalies, sulphates, phosphates and chlorides*

The value of the pyrolusite and of the other minerals depends on the-